Field
One or more embodiments of the present disclosure relates to negative active materials for a secondary battery, negative electrodes and lithium batteries each including the negative active materials, and methods of preparing the negative active materials.
Description of the Related Technology
Lithium secondary batteries are used in various applications including power sources for portable electronic products, such as mobile phones or laptop computers, as well as medium- and large-sized power sources, such as hybrid electric vehicles (HEV), or plug-in HEVs. Due to the wide application range and an increasing demand therefore, the outer shape and size of batteries are constantly changing, and as a result higher capacity, longer lifespan, and higher stability is desired compared to the small batteries.
In lithium secondary batteries, materials that enable intercalation and deintercalation of lithium ions are used in a negative electrode and a positive electrode, a porous separator is disposed between the positive electrode and the negative electrode, and then, an electrolytic solution is added thereto to complete forming the lithium secondary batteries, wherein, at the negative electrode and the positive electrode, oxidation and reduction occurs due to intercalation and deintercalation of lithium ions, thereby generating or consuming electricity.
Graphite, which is widely used as a negative active material for a secondary lithium battery, has a layered structure, which is very suitable for intercalation and deintercalation of lithium ions. Although graphite has, in theory, a capacity of 372 mAh/g, alternative electrodes to graphite are required due to the ever increasing demand for high-capacity lithium batteries. In this regard, research activity to identify a high-capacity negative active material and ways to commercialize an electrode active material that forms an electrochemical alloy of lithium ions with metals such as silicon (Si), tin (Sn), antimony (Sb), or aluminum (Al), is actively being performed. However, when silicon (Si), tin (Sn), antimony (Sb), and aluminum (Al) are charged or discharged due to the electrochemical alloy formation with lithium, a volumetric increase or decrease may occur, and the volumetric change due to repeated charging and discharging may deteriorate cyclic characteristics of an electrode including Si, Sn, Sb, and Al as an active material. Also, the volumetric change may cause cracks in the surface of an electrode active material, and when the cracks are continually formed, the surface of an electrode is fragmented, further deteriorating cyclic characteristics thereof.